Better document run_test.r (#5479)

* Better document run_test.r

* Add news bullet for #5479

* Update news/5479-better-document-run_test.r

---------

Co-authored-by: Bianca Henderson <bhenderson@anaconda.com>
Co-authored-by: Bianca Henderson <beeankha@gmail.com>

conda_build/skeletons/cran.py

@@ -115,8 +115,8 @@
     - $R -e "library('{cran_packagename}')"           # [not win]
     - "\\"%R%\\" -e \\"library('{cran_packagename}')\\""  # [win]
 
-  # You can also put a file called run_test.py, run_test.sh, or run_test.bat
-  # in the recipe that will be run at test time.
+  # You can also put a file called run_test.r, run_test.py, run_test.sh,
+  # or run_test.bat in the recipe that will be run at test time.
 
   # requires:
     # Put any additional test requirements here.

docs/source/concepts/recipe.rst

@@ -19,7 +19,7 @@ is a flat directory that contains the following files:
 * ``bld.bat`` — The build script that installs the files for the
   package on Windows. It is executed using ``cmd``.
 
-* ``run_test.[py,pl,sh,bat]`` — An optional Python test file, a
+* ``run_test.[py,pl,sh,bat,r]`` — An optional Python test file, a
   test script that runs automatically if it is part of the recipe.
 
 * Optional patches that are applied to the source.

docs/source/resources/define-metadata.rst

@@ -1127,7 +1127,7 @@ Test section
 ============
 
 If this section exists or if there is a
-``run_test.[py,pl,sh,bat]`` file in the recipe, the package is
+``run_test.[py,pl,sh,bat,r]`` file in the recipe, the package is
 installed into a test environment after the build is finished
 and the tests are run there.
 
@@ -1212,12 +1212,12 @@ following:
 Run test script
 ---------------
 
-The script ``run_test.sh``---or ``.bat``, ``.py``, or
-``.pl``---is run automatically if it is part of the recipe.
+The script ``run_test.sh``---or ``.bat``, ``.py``, ``.pl``,
+or ``.r``---is run automatically if it is part of the recipe.
 
 .. note::
-   Python .py and Perl .pl scripts are valid only
-   as part of Python and Perl packages, respectively.
+   Python .py, Perl .pl, and R .r scripts are valid only
+   as part of Python, Perl, and R packages, respectively.
 
 
 Downstream tests
@@ -1491,7 +1491,7 @@ You can test subpackages independently of the top-level package.
 Independent test script files for each separate package are
 specified under the subpackage's test section. These files
 support the same formats as the top-level ``run_test.*`` scripts,
-which are .py, .pl, .bat, and .sh. These may be extended to
+which are .py, .pl, .r, .bat, and .sh. These may be extended to
 support other script types in the future.
 
 .. code-block:: yaml

news/5479-better-document-run_test.r

@@ -0,0 +1,19 @@
+### Enhancements
+
+* <news item>
+
+### Bug fixes
+
+* <news item>
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* Better document `run_test.r`. (#5479)
+
+### Other
+
+* <news item>